[1] Univ Alabama Birmingham, Div Pulm Allergy & Crit Care Med, Birmingham, AL 35294 USA
[2] Univ Zurich, Dept Publ & Global Hlth, Epidemiol Biostat & Prevent Inst, Zurich, Switzerland
[3] Univ Alabama Birmingham, Gregory Fleming Cyst Fibrosis Res Ctr, Birmingham, AL 35294 USA
[4] Univ Alabama Birmingham, Comprehens Ctr Hlth Aging, Birmingham, AL 35294 USA